Did the test after a short city drive there (about 20 minutes stop and go at about 35mph)

Car is a 94 sentra with: Stillen pop filter, 4-2-1 header (the qg18 header) with egr and O2 in the same exhaust runner (that the egr is being pulled from [4]).

Timing is at ~10 degrees (set with the guide on here). The plugs were, and still are, a light tan color with minimal carbon on them (only on cylinder 1 and 4). I replaced all 3/16 vac lines, new ntk O2, new ngk wires, ngk plugs gapped to .43 with about 5k, cleaned the plugs/connectors for everything around the oil fill cap w/ acetone (accidentally left it off for a 30 mile drive), replaced the cap and rotor about 5k ago, and checked the resistance for the coil (which was 1 ohm and 13.3k ohm). I also reset the ecu and it threw no cel's. The water pump leaks coolant and when the system gets a bubble in it the car will run poorly until 4K. Then I went back to the Emissions place and failed again. Here are the numbers:

HC 326 CT limit 188
CO .03% CT limit 1%
NOx 2136 CT limit 2188

Car was hot (just finished a 30 minute highway trip) so that may be why the numbers are so different.

Any ideas where to look next? I have some ideas but would like others input (and don't want to influence your opinion). Thanks!

High HC - not burning all the gas, bump up the timing a couple degrees could help it burn a bit better, but, that could raise the NOx numbers a bit.

High NOx - cat's not working efficiently and/or EGR isn't working right. Clean the passages.

You said "when the system gets a bubble in it the car will run poorly until 4K". I assume you mean the cooling system and 4,000 rpms, about the same time the ECU will go into open-loop and ignore the O2 sensors. Why does it get a bubble in it in the first place? You got a head gasket not sealing or something along those lines?

Switching over to a "cooler" plug might help the NOx's drop a bit, but would probably make the HC numbers worse.
Does your cat have an air tube that's supposed to feed it a bit of extra raw air while it's running?

99% of the questions that are "STRANGE" have a dirt simple answer...usually answered by a dirt simple search.

Why do people continue to run a vehicle when a warning light comes on or starts flashing? Isn't that a clue that something is wrong and you probably should NOT drive it?
Is this whole car driving thing really freekin' brain surgery?

Here's something new for the crowd/clowns...
"A little bit of Google goes a long way!"

Ever notice the one post wonders for info on turbo'ing a GA16 are never heard from again after they figure out the cost???

High HC - not burning all the gas, bump up the timing a couple degrees could help it burn a bit better, but, that could raise the NOx numbers a bit.

The timing was at 8 after the second failing, I adjusted it to 12 and it doesn't seem any better.

Quote:

Originally Posted by jdgrotte

High NOx - cat's not working efficiently and/or EGR isn't working right. Clean the passages.

I'll double check the tube, but I flexed the egr diaphragm and stalled the car then I pulled the vacuum line off and there was no vac so all signs point to adequate. When I revved the engine I didn't feel the diaphragm move nor did I feel vac out of the vacuum line.

Quote:

Originally Posted by jdgrotte

You said "when the system gets a bubble in it the car will run poorly until 4K". I assume you mean the cooling system and 4,000 rpms, about the same time the ECU will go into open-loop and ignore the O2 sensors. Why does it get a bubble in it in the first place? You got a head gasket not sealing or something along those lines?

Yep, cooling system and the bubble comes from the coolant pump pumping coolant all over the road/driveway/parking lot.

Quote:

Originally Posted by jdgrotte

Switching over to a "cooler" plug might help the NOx's drop a bit, but would probably make the HC numbers worse.
Does your cat have an air tube that's supposed to feed it a bit of extra raw air while it's running?

There is an air tube on the side of the car but it is plugged. I also looked inside the cat and the matrix is intact and a light gray color.

Also there is no check engine code being thrown. I would think if the O2 was not working there would be a cel. One other detail I forgot to mention is the idle is lumpy, like it isn't hitting on all cylinders/has some mean cams but it sounds to be the correct rpm's (no tach). Lastly when I went to check the timing a second time the car pooped out the first attempt (after revving it to 3k 3 times).

Thanks for your speedy input man! I appreciate it, I only have 10 days to get this emissions thing licked so I am doin what I can to figure it out.

when checking your egr on the nissan sentra hook a vacuum gauge up the vacuum line and you have to drive the car to see if its pulling vacuum. If its not... your gonna have a bad day . Also there is another vacuum line below the egr and its rips/tears really easily and will cause nox to go up. one last thing is that even though you pull up on the diaphram and make it stall in idle doesnt mean its working correctly under load. the egr pipe off the exhaust manifold on Nissan cars sometimes almost gets sealed shut and needs to be cleaned. Happened to me . Im not sure what the ohms should be on injecters sorry ;[

Resistance spec on the fuel injector should be approx. 10 ohms. You should definately replace the #2 injector. You can get one through any Nissan or auto parts store; it will be a lot cheaper on the aftermarket.

I'll double check the tube, but I flexed the egr diaphragm and stalled the car

At least you know the EGR exhaust passages are fairly cleared out.

Quote:

then I pulled the vacuum line off and there was no vac so all signs point to adequate.

Adequate? Quite possibly IN-adequate.

Quote:

When I revved the engine I didn't feel the diaphragm move nor did I feel vac out of the vacuum line.

I'd doubt you feel or see it just sitting there and revving it since the EGR basically only opens up under part throttle cruise conditions. Some engines, yes, a little bit at idle, but in general, EGR is closed at idle and heavy loads.

Quote:

Yep, cooling system and the bubble comes from the coolant pump pumping coolant all over the road/driveway/parking lot.

There's an issue for ya

Quote:

There is an air tube on the side of the car but it is plugged. I also looked inside the cat and the matrix is intact and a light gray color.

Plugged air tube? Going into the cat? Not enough fresh air (whether it's coming from the cylinders or an outside source) = no good.

Quote:

Also there is no check engine code being thrown. I would think if the O2 was not working there would be a cel.

CEL's basically have to be taken with a grain of salt...at best. Only a fool trusts the CEL 100% of the time...whether it's on OR off.

Quote:

One other detail I forgot to mention is the idle is lumpy,

That's a helluva detail to skip out on.

Quote:

Coolant temp sensor: hot is 388 ohm's and cool is 1.6k ohms

That looks OK-ish, but I would expect the cold reading to be a bit higher, unless the temp wasn't really all that cold.

Quote:

Pulled plug wires 1-4 while car was running. #2 had no effect on the idle, all the others made the car nearly stall.

Bingo #1

Quote:

Then I checked the resistance of the injectors (three out of four): #1 12.2 ohms #2 181 ohms #4 11.9 ohms

Bingo #2

Quote:

So I am going out on a limb and am going to say my #2 injector is shot or on its way there. Do you agree with my diagnosis? If so have any recommendations as to where I can get some new ones?

#2 not firing right = rich mix going out the exhaust, O2 sensor picks that up and leans out the whole thing to compensate. Now not only is #2 misfiring, but the rest of them are probably on the verge of a lean misfire. #2 = puking raw fuel (high HC), 1-3-4 running lean pushing out too much raw air (High NOx from running too hot).

Quote:

Originally Posted by astroboy

I am going to try to get a set of four and have them cleaned and flowmatched. That'll cost me the same amount as a new one from the stealership.

I think flow matching is a waste of money unless you are going for all out crazy performance, trying to eek out that last .1HP. Especially in a 1.6.

99% of the questions that are "STRANGE" have a dirt simple answer...usually answered by a dirt simple search.

Why do people continue to run a vehicle when a warning light comes on or starts flashing? Isn't that a clue that something is wrong and you probably should NOT drive it?
Is this whole car driving thing really freekin' brain surgery?

Here's something new for the crowd/clowns...
"A little bit of Google goes a long way!"

Ever notice the one post wonders for info on turbo'ing a GA16 are never heard from again after they figure out the cost???

"I think flow matching is a waste of money unless you are going for all out crazy performance, trying to eek out that last .1HP. Especially in a 1.6."

Yeah, have to agree with that. You can pick up a reman. Beck/Arnley fuel injector for $65 (after core) from Advance Auto Parts or for $30+shipping at RockAutoparts.com. Nissan MSRP is $150 for a new injector.

#2 not firing right = rich mix going out the exhaust, O2 sensor picks that up and leans out the whole thing to compensate. Now not only is #2 misfiring, but the rest of them are probably on the verge of a lean misfire. #2 = puking raw fuel (high HC), 1-3-4 running lean pushing out too much raw air (High NOx from running too hot).

It is #2 that's running rich (during idle) and normal under wot (at least this is my theory) because it seems to run on all cylinders when driving hard and the plug wasn't carboned out/burnt out. The O2 is in cylinder #3 so the ecu never knows it is faulty.

Quote:

Originally Posted by jdgrotte

I think flow matching is a waste of money unless you are going for all out crazy performance, trying to eek out that last .1HP. Especially in a 1.6.

Ok, then I'll just go by resistance readings or something. Thanks again guys!

It is #2 that's running rich (during idle) and normal under wot (at least this is my theory) because it seems to run on all cylinders when driving hard and the plug wasn't carboned out/burnt out. The O2 is in cylinder #3 so the ecu never knows it is faulty.

I missed the part about the 4-2-1 headers up top, and this is exactly the case why I WON'T run something like that. One of the other cylinders takes a dump, which as luck would have is the one that has the O2 sensor in it, and screws it up for the rest of everything.
Also, as noted above, the color of the cat...well, that's a crap shoot at best. Unless you've got another cat EXACTLY like the one you're looking at, who's to say what color it really SHOULD be.
Of course if the mesh (matrix, whatever you want to call it) is good, it's a good sign that the cat hasn't self destructed...BUT...has it melted down internally? Can't really tell that so well from a visual without cutting it apart.

99% of the questions that are "STRANGE" have a dirt simple answer...usually answered by a dirt simple search.

Why do people continue to run a vehicle when a warning light comes on or starts flashing? Isn't that a clue that something is wrong and you probably should NOT drive it?
Is this whole car driving thing really freekin' brain surgery?

Here's something new for the crowd/clowns...
"A little bit of Google goes a long way!"

Ever notice the one post wonders for info on turbo'ing a GA16 are never heard from again after they figure out the cost???

"I think flow matching is a waste of money unless you are going for all out crazy performance, trying to eek out that last .1HP. Especially in a 1.6."

To once again be a wet blanket as usual ......................... I would like to see ANY shop "flow match" ANY arbitrary 4 sealed injectors (ala the Nissan ones and just about any other I have bumped into too) I slap down in front of them - at best they can "clean them" and you end up with a matched set of pristine injectors ito cleanliness ..................... there is but squat they can do to these things to ensure the weight of the needles (and thus mechanical lag/response) are all exactly the same, the pintle spray patterns are identical, the radial wear on the needle points are the same, coil resistance match ayda yada yada ................... UNLESS YOU SEE THEM CUTTING AND RE-WELDING THE WHOLE ASSEMBLY ONCE ITS BEEN "MATCHED" ........................... and I have yet to even hear of a machine shop attempting to match injectors economically this way.

Economically being the key word.
I was at a school for circuit card rework a few years ago, happened to get a chance to talk with a couple of guys that worked at Pratt&Whitney, in the rocket engine division. Got to talking about turbo-pumps, LH2/LO2 injection, spray patterns, amongst other neat stuff. They were saying that while they strive for absolute perfection and getting that last 1% of absolute tolerance in parts matching, most of the time, for an example, they end up having a batch of say 100 injectors made, and match them in groups. So, one group will be within a couple percent of each other, but the next group will be within a couple percent of each other also, but might be a couple of percent higher than the previous group. The engines are overbuilt anyways, and they can compensate for overages and/or shortfalls in other ways to keep the engines performance within an overall tight tolerance.

In other words, it's all about money...

99% of the questions that are "STRANGE" have a dirt simple answer...usually answered by a dirt simple search.

Why do people continue to run a vehicle when a warning light comes on or starts flashing? Isn't that a clue that something is wrong and you probably should NOT drive it?
Is this whole car driving thing really freekin' brain surgery?

Here's something new for the crowd/clowns...
"A little bit of Google goes a long way!"

Ever notice the one post wonders for info on turbo'ing a GA16 are never heard from again after they figure out the cost???

Economically being the key word.
I was at a school for circuit card rework a few years ago, happened to get a chance to talk with a couple of guys that worked at Pratt&Whitney, in the rocket engine division. Got to talking about turbo-pumps, LH2/LO2 injection, spray patterns, amongst other neat stuff. They were saying that while they strive for absolute perfection and getting that last 1% of absolute tolerance in parts matching, most of the time, for an example, they end up having a batch of say 100 injectors made, and match them in groups. So, one group will be within a couple percent of each other, but the next group will be within a couple percent of each other also, but might be a couple of percent higher than the previous group. The engines are overbuilt anyways, and they can compensate for overages and/or shortfalls in other ways to keep the engines performance within an overall tight tolerance.

In other words, it's all about money...

Ah yes - but that is "matching" by selecting units with the same or close parameters once they are assembled (and still sealed) .................... if the "matching" service centre on any 4 injectors I slap down in front of them need to have a stash of 100s of injectors of every kind of injector they "match" from which to chose 4 to return to me as "matched" then imo its also still a crap-shoot ito age and distances covered - and the main reason why one often get a failed "service" or "matched" injector being reported.

........................ I can probably do a better job of "matching" injectors (or then causing an actual noticeable effect/result) by mechanically removing the gunk and carbon from the combustion chamber/vales/IM/TB

.......... and for the record - the same argument goes for a so called "reman" injector because there is simply no way to "reman" ANY ARBITRARY INJECTOR I PUT DOWN ON FRONT OF THE REMAN-SHOP COUNTER. Anybody want some nice pics of what an actual injector looks like inside and why I comment as I do above (I cut it open and documented the inner design of an actual Nissan injector) I can post it here - huge high-res pics though